Update of FROGS and adaptation to PEARL 4.4.4 and FOCUS
groundwater II guidance
Loiseau, L. 1, Beigel, C. 2, Cecchi, M. 1, Garcia, L2., Guyot, C. 3, Hammel, K. 3,
Knowles, S. 4, Obeidy, C. 1, Reiher, W. *5, Schubert, S. 4, Shbaita, H 2
1
Syngenta, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
BASF, Speyerer Straße 2, 67117 Limburgerhof, Germany
3
Bayer CropScience, Alfred-Nobel-Strasse 50, 40789 Monheim, Germany
4
Dow AgroSciences, 3B Park Square, Milton Park, Abingdon, Oxfordshire, OX14 4RN, UK
5
Dr. Knoell Consult, Marie-Currie-Str. 8, 51377 Leverkusen, Germany
* [email protected]
2
FROGS (French Refinement of Groundwater Scenarios) is a PEARL-based simulation tool
considered as a higher-tier option within the authorization process for plant protection
products in France. The current FROGS 2.2.2.2 (FROGS 2011) is based on PEARL 3.3.3
and was published in July 2011. Meanwhile, the new FOCUS-PEARL 4.4.4 has been
released, which incorporates various updates and amendments recommended by the
FOCUS groundwater group (FOCUS 2009). Consequently, the FROGS development group
decided to update the tool to (i) adapt it to PEARL 4.4.4, (ii) integrate the adaptations from
FOCUS (2009) that were considered to be appropriate and meaningful to the specific
FROGS assumptions and (iii) improve the method for allocating crop surfaces.
Inclusion of PEARL 4.4.4 and its new hydrologic model version of SWAP 3.2.34
Technically, the main change in FROGS to adapt it to PEARL 4.4.4 is the adaptation of the
input template file. This update eliminates crashing of PEARL runs (9 out of 1481 scenarios
aborted in the previous FROGS version due to a problem with the former SWAP version) so
splitting of rainfall events over several consecutive days in selected scenarios is no longer
required and allowed the inclusion of 4-year crop rotations.
Adaptations to the FOCUSgw II guidance implemented in FROGS 3.3.3.3

The most appropriate method for calculating reference evapotranspiration for
Southern European scenarios and conditions according to FOCUS, 2009 is
considered to be the FAO method. As France belongs to the Southern regulatory
zone, this method was implemented.

In accordance with FOCUS (2009) harmonisation of the implementation of crop
factors, which are needed for the calculation of actual evapotranspiration, was
adopted.

80th percentile PECgw is calculated according to FOCUS (2009) based on the annual
average of the 16th & 17th highest PECgw values.
Some points that changed in FOCUS (2009) compared to the former guidance have not
been adopted. Thus, the extensive method in which realistic irrigation amounts were
identified for the previous FROGS version was kept and the adaptation of rooting depth up to
the target depth was not considered relevant since rooting depth was already limited to the
target depth in the previous version of FROGS.
Additional updates implemented in FROGS 3.3.3.3

New mitigation template to enable mitigation based on soil pH.

Finally, the approach to allocate crop surfaces within the agronomic units (AU) was
improved: the surface of each combination of soil, crop and AU is now estimated
using the cultivated area of each crop within each AU (based on the 2000 agricultural
census), the distribution of soils in the cropping region and the area of each soil
within each AU. This results in ca. 25% fewer scenarios (1097 in total in FROGS
3.3.3.3) and in a more accurate total area modelled for each crop.
Results
Test runs were conducted with FOCUS dummy substances D, C and Met-C to evaluate the
overall effect of the changes. Example results are provided in Figure 1.
Figure 1. Cumulative areal distribution of PECGW for some selected combinations of crops (MG: grain
maize, SB: sugar beet) and Compounds (FOCUS Dummy substances C and D, Metabolite of C).
Conclusions
FROGS was updated to reflect a more appropriate allocation of crop surfaces, current
European guidance for groundwater modelling (FOCUS 2009) and PEARL model
enhancements to meet the current status implemented in the regulatory groundwater
modelling framework for pesticide authorisation at EU level. Test simulations show that the
cumulative areal distribution of the 80th temporal percentile PECgw is slightly impacted by the
modification included in FROGS 3.3.3.3. The main impact is introduced by the modification of
the crop surface allocation (see right graphs in Figure 1).
The new FROGS 3.3.3.3 and the corresponding updated version of the FROGS report
(FROGS 2013) outlining all the amendments in detail will be made available soon on the
FROGS webpage (http://frogs.eclosion-share.net).
References
FOCUS (2009). Assessing potential for movement of active substances and their metabolites
to ground water in the EU. Report of the FOCUS Ground Water Work Group, EC Document
Reference Sanco/13144/2010 version 1, 604 pp.
FROGS (2011). “French Refinement Of Groundwater Scenarios” Report of the UIPP
Environmental Methodology Working Group version 2.0, 314 pp.
FROGS (2013). “French Refinement Of Groundwater Scenarios” Report of the UIPP
Environmental Methodology Working Group version 3.0. (in preparation).